At the present time electronic calculators are used for a multiplicity of purposes by engineers, accountants, students and others. The price of such electronic calculators varies widely, depending upon the complexity of their functions, the number of functions they perform, whether they provide a print-out, the number of digits which they display, and other factors. For example, small hand-held calculators would include calculators which simply add, subtract, multiply and divide and display only six digits, which may cost as little as $25.00, to calculators costing many hundreds of dollars which perform engineering functions or provide a tape print-out.
There have been various suggestions as to how electronic calculators may be secured against theft or loss by being borrowed and not returned. It has been suggested that the calculator may be permanently fitted into a casing, which casing is securely fastened to a desk or other piece of furniture. Of course, such security provision prevents the portability of the calculator. It has also been suggested that the casing may be made removable and lockable. When the calculator is to be moved, the lock must be unlocked by a key or a combination and the calculator removed from the casing.
These provisions against theft have proven to be cumbersome and inefficient. For example, an engineer, during his travels within a plant, may move from one location to another and frequently wishes to have his hand-held calculator with him. He may, during the day, put it down temporarily in any number of locations. As long as the calculator is unlocked from its casing, it is subject to theft or being borrowed and not returned.
A similar problem may arise in connection with computer terminals, electric typewriters and other electric keyboard instruments such as the computer terminal of the alphanumeric type. In these instruments some provision may be desired to prevent theft of the instrument or to prevent unauthorized use of the instrument, for example, unauthorized use of the computer terminal. The conventional method used for such security is to chain, or otherwise lock, the terminal with its cover closed or to chain or otherwise lock the instrument to a piece of furniture. These measures are subject to the faults of a conventional lock, namely, the locks may be picked, the keys lost, and the unlocking of the device may be time-consuming and cumbersome.